Bull-blocks



Aug. 30, 1955 E. F. scHwElcH l-:TAL 2,716,482

BULL-BLOCKS Filed Jan. 14, 1952 3 Sheets-Sheet l Il 2 f7' fff/ E g 3 77 y; Z4 INVENTORS F|G.|.A EDWARD F. ScHwElcH SANFORD A. SILVERSTEIN JOSEPH W. GOLDENBERG Aug. 30, 1955 E. F. scHwElcH ETAL 2,716,482

v BULL-BLOCKS Filed Jan. 14, 1952 3 Sheets-Sheet 2 FIG. 2. 7

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. JNVENToRs EDWARD F ScHw-:IGH SANFORD A. SILVERSTEIN JOSEPH W. GoLDENBl-:RG y WH Aug. 30, 1955 lE. F. scHwElcH ET AL. 2,716,482

BULL-BLOCKS 3 Sheets-Sheet 5 Filed Jan. 14, 1952 l; D ul FIG. 6.

INVENToRs EDWARD F. ScHwl-:lcH SANFORD A. SILVERSTEm JOSEPH W. GOLDENBERG W rfa/swff/ United States Patent O i BULL-BLOCKS Edward F; Schweich, Clayton, and Sanford A. Silverstein, University City, Mo., and Joseph W. Goldenberg, East St. Louis, Ill., assignors to Lewin-Mathes Company, St. Louis, Mo., a corporation of Missouri Application January 14, 1952, Serial No. 266,364

5 Claims. (Cl. 205-3) This invention relates in general toV certain new and 1.

useful improvements in tube drawing machinery and, more particularly, to a type of tube drawing machinery sometimes referred to as a' bull-block.

In the drawing of seamless tubing from pierced billets of a malleable metal, such as copper for instance, it is a common practice to pull the pierced billet through a large reducing die in a draw bench and pass the tubing through successive drawing dies of successively smaller diameters until the tube is reduced to the .desired diametral size and wall-thickness. operation, of course, results in a progressive lengthening of the tube and consequently draw benches for producing such tubing are extremely long, requiring relatively large oor space. The straight-line draw Ybench also produces straight lengths of tubing which are somewhat 1 The drawing drawing die and engaged in a suitable jaw mounted upon the drum. The drum is then rotated by apowerful driving ymechanism and thus serves to pull the tubing through the drawing die while causing it to wrap up around the outer peripheral surface of the drum. The gripping jaw is usually mounted for axial sliding movement along the drum as the tubing winds thereon so that successive turns of tubing will force the previously drawn turns -of tubing upwardly along the surface of the drum until i the draw is completed. In order to facilitate this winding and self-feeding action, the drums frequently are tapered slightly.

Bull-blocks, as these ymachines are called, have definite advantages in terms v:of space requirements and, furthermore, the tubing thus drawn is already coiled so that it vcanbe very .conveniently fand simply handled. Nevertheless, the tubing thus produced 'is not entirely satisfactory .because the cross-sectional shape is slightly oval. This ovality, which Ais highly undesirable in tubing, is not particularly .serious .in small diameter tubing .and in ,tubing having relatively heavy wall size, particularly where the ratio -of the drum diameter to the tubing diameteris 'relatively great. Gn the other hand, where `large diameter ytubingis `being drawn or vthe wall vthickness of the Itubing yis relativelyzsmallin 'relation to tubing -diameter, the `tendency toward ovality becomes Aquite gpronounced.

Another difficulty `which'ha's been encountered with conventional types of bull-blocks is `the' difficulty of obtaining:accuratefmeasurementsas to 'the length of tubing 'in 'the coil' 'after it has been drawn. Supertcially ,it

2,716,482 Patented Aug. 30, 1955 would seem that in a bull-block or drumv o f given diameter it should be possible tov ascertain within reasonably accurate limits e length of tubing in the coil by counting the numbe of turns on the block or drum. Unfortunately, however, vin `the course ofk normal vrota,- tion, the coils ordinarily do not lie in closely adjacent relation but tend to angle away fromeach other and, therefore, it becomes diicult and inconvenient vto determine the length of tubing which may happen to be in any particular coil. It has been found `that variations in length amounting to several percent are routinely encountered in conventional bull-block drawing opera*- tions. Since seamless tubing and, particularly, seamless tubing formed from non-ferrous metal,- is comparatively expensive, this degree of errorY in length measure'- ment is highly unsatisfactory both to the manufacturer and the purchaser or user.

It is, therefore, the primary object of the present irrvention to provide a tube drawingmachine of `the bulliblock type which is capable loi." drawingf'seamless tubing at a relativelyhigh rate of speed without producing any ovality or other undesirable deviations from the true desired crosssectional shape 'in the tubing being drawn.

It is another object of the'present invention to prdvide a tube drawing machine of the type `stated `in which it is possible to determine, witha high degree of ac"- curacy, the length of tubing in any particularycoil on the basis of the number of turns in fthe coil' as it is being drawn. v

It is another object` ofthe present vinventionfto vprov ide a tube drawing -machine 4of the type stated v which vis rugged, durable, and can be operated continuously for long periods of time `without requiringV yextensive maintenance or repairs.

It isa Vfurther object of the present invention to provide a tube drawing machine of the't-ype stated which is simple in operation `and ca n be readily manipulated and controlled by a single operator. i

It is an additional object of the present invention to provide ka tube` drawing machine Vofthe type stated which may readily and simply be converted for'the'ac'- commodation of various :different sizes" of ytubing to be `drawn thereon without necessitating.@me-consuming and expensive mechanical set-up operations.

With the above .andl other :objects i-n view, 'o`ur `invention residesin the novel features o'f form, construction, arrangement and combination yof Ipart-s presently 5described and `pointed out `in the Claims. i

ln the accompanying drawingsil Figure 1 isa top plan view of a bull-blockconstructed in accordancewith :and .embodying the present invention;

Figure 2 is afr`ont elevational-view, partly v-brolf'ren away and insection, of the bullfb'locky f Figures 3 and' 4 are .transverse sectional views taken along lines 3 3 and 4 4, respectively, lofiFigure 12v;`

Figure 5 is a fragmentary sectional :View similar to Figure 4, but showing the vdrum and? tube-gripping jaw in an advanced .position as the initial fpo'rtionof the tubing is being drawn Vagainst the drum; i

Figure 6 i`s`afr`agmentary sectional view .taken'alon'g line v6-6ofFigu're 5;n 'Figure 7'is afragmentary sectional 'view' -taken `along line 7--7 of .Figure 2;.and i i Y .Figure '8` is`a schematic wiring diagram' showing the electrical connections lof the several component elements ofthe presentinventiongf Referring nowin` more detaily :and 7byA reference Vcharacters to the drawings, which illustrate apreferred embodiment of ithe present invention, A `designates a ibullblock comprising a :relatively fheavyhorizontal bed plate 1 provided around -itsperipheral margin withtlepending flanges 2 for-engagement Vwiththe `ylloor orrotfhersupporting surface. Welded around the peripheral margins of the bed plate 1 and extending vertically upwardly therefrom are side walls 3 and corner posts 4 formed of heavy gauge angle iron. Supported upon and extending horizontally across the upper ends of the corner posts 4 is a base plate 5 having a relatively large aperture 6 opening vdownwardly into the enclosure or space s forming the interior of the machine base.

Formed integrally with or otherwise rigidly mounted upon the upper face of the base plate 5 is a large, heavy, extremely rigid head-frame 7 of substantially inverted U-shape and being provided with an enlarged housing 8 registering with and enclosing the aperture 6. Securely mounted within the base-enclosure s upon the bed plate 1 is a conventional speed reducer 9 having an output shaft 10 and an input shaft 11, the latter being connected through a conventional coupling 12 to a so-called clutch -motor 13, which includes, in combination, a heavy-duty electric motor directly connected to a mechanical clutch ,and brake so arranged that immediately upon interruption of the electrical circuit to the motor the clutch will automatically disengage and the brake will automatically become operative to stop the motor drive shaft 14 practically instantaneously.

The housing 8 is provided with an upwardly presented recess 15 having a horizontal bottom wall 16 provided with a central aperture 17. The recess 15 is closed across its top by a cap plate 18 having a central aperture 19 vertically aligned with the aperture 17 and being adapted for retaining a pair of conventional roller thrust bearings 20 for operatively supporting a vertical shaft V21 which projects downwardly and is connected by means of a conventional shaft coupling 22 to the output shaft 10 of the speed reducer 9. Also rigidly but removably mounted upon the output shaft 10, just below the shaft coupling 20, is a split-hub sprocket 23.

At its upper end the shaft 21 passes through a conventional ball-bearing journal 24 and is provided with a removable sprocket 25 which is, in turn, connected by means of a sprocket chain 26 to a large drive-sprocket 27 removably secured upon the upper end of a drum shaft 28 journaled in and extending vertically through the central portion of the bight 29 of the head frame and terminating at its lower end in a shaft-tail 30 of rectangular cross section for snug-fitting non-rotative engagement within a cylindrical drum 31, the latter being counter-bored upon its opposite horizontal end faces to provide clearance recesses 32, 33. The shaft-tail 30 projects downwardly into the clearance recess 33 and is threaded at its lower end, as at 34, for receiving a retention nut 35 by which the drum 31 is securely, but removably, mounted to the shaft 28. Upon its external or peripheral face the drum is precisely machined to provide a closely lying continuous helical groove 36 of substantially semi-circular cross-sectional shape and having a diametral size equal to the outside diametral size of the tubing to be drawn.

Mounted upon the forward face of one vertical leg of the U-shaped head frame 7, on the opposite side of the drum 31 with respect to the shaft 21, is a pair of spaced parallel way-bars 37 forming a dovetail slideway 38 for shiftably accommodating a slide-block 39 operatively mounted therein. Extending threadedly through the slide-block 39 and centrally along the slideway 38 is a feed screw 40 which is turned down and journaled at its upper end in a sleeve bearing 41. At its other end the feed screw 4t) is turned down and similarly journaled in a horizontal bracket plate 42 formed integrally with and extending forwardly from the head frame 7. Below the bracket plate 42 the feed screw 40 is provided with an integral shaft portion 43 which extends through a suitable bearing 44 mounted in the base plate 5 and extends through the driven member 4S of a magnetic clutch 46 having a driving member 47 disposed concentrically around the driven member and provided upon its peripheral face with a sprocket 48 which is, in turn, drivingly connected by means of a sprocket chain 49 to the sprocket 23. The shaft portion 43 of the feed screw 40 extends downwardly below the driven member 45 of the magnetic clutch 46 and is, at its lower end, connected by means of a conventional coupling 50 to the drive shaft 51 of a small high-speed die-return motor 52 which is, in turn, mounted upon an upstanding support-post 53 within the base enclosure s.

Formed integrally with the slide-block 39 and `projecting horizontally forwardly therefrom is an arm 54 reinforced by an integral gusset 54'. Mounted upon the upper face of the arm 54 for swivelling movement about a vertical swivel pin 55 is a U-shaped die-carriage 56 and operatively mounted therein for rocking movement about a horizontal axis is a tubular drawing die 57 having oppositely presented axially aligned pins 58 rotatably engaged in the opposed parallel side walls of the U-shaped die-carriage 56, all as best seen'in Figure 7. The drawing die 57, the slide-block 39 and the arm 54, are all so arranged and positioned that the mouth 57 of the drawing die 57 will be positioned at the level of the lowermost convolution of the helical groove 36 when the slide-block 39 is in its lowermost position resting upon the bracket plate 42, substantially as shown in Figure 2.

The drum 31 is provided adjacent its lower end with a radially inwardly extending somewhat rectangular recess 59 coinciding substantially with the entrant or lower end of the helical groove 36 and swingably mounted upon the under face of the drum 31 for rocking movement in a horizontal plane is a gripper arm 60 having a lateral extending horizontal enlargement 61 which is provided with a pair of converging slots 62, 63. `Shiftably mounted in, and extending upwardly through, the slots 62, 63, are slide-blocks 64, 65, respectively, provided on their upwardly extending ends with deeply serrated gripper jaws 66, 67, respectively. The gripper jaws 66, 67, are somewhat shorter in height than the vertical height of the recess 59 so that the gripper jaw 66 will fit freely within the recess S9 when the gripper 60 is swung inwardly into the position shown in Figures 5 and 6.

Mounted upon the bracket plate 42 in laterally spaced relation to the slide-block 39 is a limit switch 68 having an actuating element 69 projecting outwardly therefrom into the path of a contact boss 70 formed on the slideblock 39 and adapted to be actuated as the slide-block 39 reaches the lower limit of its travel. Similarly mounted adjacent the upper end of the slideway 38 is a second limit switch 71 having a laterally projecting actuating arm 72 for similarly contacting the boss 7 0 of the slideblock 39 as the latter reaches the upper limit of its travel. It will be noted, in this connection, that the upper end of the feed screw 40 is turned down for a substantial distance and is free of threads so that in the event that the slide-block 39 should, for some accidental reason, move upwardly past the upper limit switch 71 or the latter should fail to function, the slide block 39 will, in effect, run oif the threads and idle so that no serious damage will result to the machine or any of its component parts.

Similarly mounted upon the forwardly presented face panel 3 of the machine base is a main control switch 73 of substantially conventional design and including a main switch button 74, a die-return switch button 75, and a stop-switch button 76. The main switch button 74 controls a conventional double pole single throw relay 77 having a hold-in coil 78. 'Ihe die-return switch button 75 actuates a double-pole single throw relay 79 having a hold-in coil 80, and the stop-switch button 76 is operatively associated with a single pole single throw switch 81, the switch blade of which is normally spring-biased to closed position. It will be noted that the limit switches 68, 71, are similarly single pole single throw switches with switch blades normally spring-biased to closed position and, like the switch 81, are opened responsive to mechanical actuation. It will also be noted by reference vto the wiringdiagra'rn-,Wigure '8,1' tltat'ftire limit switch 71 and the stop switch'81'1are in :with each -other and in -serieswith the holding coil '78 ofy 'the relay 77. Similarly the 'lower limit switch 68 iis in series with the holding c'oil 580 Aof the -relay lv79. The 4dieLreturn motor 52 is, furthermore, `connected tothe rA. C. line through the relay 79 andthe `ni'i'an motor2and`magnetic clutch are connected in' parallelto the A.' C. Aline through the relay 77. Finally, the circuit includes 'a safetyinterlock relay 82 which consists ofan lactuatingl'coil 183 and la single pole single throw switch S, the switch blade of which -is normally lsptingibiased to `closed position. The holding coil 83 is parallel' across the-common lead lto 84 is in series with the die-'return motor` '52.

In use, the operator manually inserts 'the swaged or pointed end of a'-len'gthfo"f tubing stock -t through the drawing die 57 and engages 'itfbetwe'en the gripper jaws the main motor 13 and magnetic' clutch "46 and the switch 66, 67, with the gripper arm 60fswung` outwardly and the drum 31 rotated to the position shown in Figure 4. A slight tightening pull -either on the gripper arm 60 or backwardly upon the tubing -t will serve t`o pull the grip# per jaws 66, 67, along the lconverging slots 62, 63, and tighten them upon the pointed end of the tubing -t.' Thereupon, the operator manually presses the main switch -button 74 closing the mainrelay 77 and 'energize ing both the main motor 13 Vand the magnetic clutch'f46. Since the slide-block 3'9-is in its vlowerxnost position and the boss 70 is in engagement Aagainst Ithe" 'actuating arm 69 of the lower limit switch 68,7ths latter switch' is held open. Thus, the circuit t'o the die-return motor 52 is open and the die-return motor S2 :is accordingdy not energized. Immediately upon closing the main relay 77, however, the -holding coil 83 of the safety interlock relay 82 is energized," opening the Aswitch 84 'and doubly assuring that the circuit to the die-return `motor 52 will remain open so that the die-return motor i52wil'l notfbe energized while the relay 77'is closed. vAsthe lmotor 13 takes up rotation, the shaft 2 1 is vrotated simultaneously driving the drum 31 through VVthe sprocket ychain 26 and the driving member 47 Vof the magnetic clutch-46-through the sprocket chain 4'9. Since the magnetic clutch -is also energized and hence coupled, thev driven member 45 will also be rotated, thereby rotating the feed 'screw 54'02and feeding the slide-block 39 `upwardly in precisely timed relation to the rotation ofthe drum 31. As the `drum 31 takes up rotation the gripper arm 60 will move from the position shown in Figure 4 to the .positionsliown in Figure 5 in which the gripper jaw 66 lies within therecess 59 and the initial portion of the tubing t is vthus laid precisely into the entrant portion of the groove 36.

The speed of rotation and pitch ofthe feed screw 40 is such that the drawing die S7 will ride upwardly in precise following relationship to the .helical groove 36 so that as .the drum 31 rotates .and pulls the; tubing l through the drawing disc 57 the oncoming portions of tubing will fall precisely in and follow the groove 36. Since the groove 36 is substantially semi-circular itxwill embrace the side walls of the tubing t as it bends around and conforms to the circularity of the drum 31, thereby preventing any distortion in the true circular crosssectional shape of the tubing t and forcing the tubing t to lie in closely contiguous uniform turns or convolutions.

The vertical height of the drum 31 and the number of convolutions in the groove 36 are ordinarily selected so that the drum 31 will more than accommodate the usual lengths of tubing to be drawn. Thus, in the ordinary run of operations the entire length of the tubing t will be drawn through the drawing die 57 before the drum is entirely filled up. As soon as the final portion of the tubing t passes beyond the mouth 57 of the drawing die 57 the tension will immediately be released and the tubing will spring outwardly uncoiling itself somewhat, thereby releasing the drawing tension on the gripper jaws 66, 67 This release of tension will cause the gripper jaws'66, 767, to loosen their grip upon the tubing tand the Aentire coil will fall downwardly free of the drum 31 coming to rest upon the upper face of the base plate 5 from which it may be manually removed by the operator for further processing or handling. 4If the tubing t is to be drawn through a successive operation to lfurther reduce its external diametral size it may be transferred to such further processing equipment or -if the tubing is at it-s final and finished size it 'can be transferred to other parts `of the'plant and annealed, inspected, packaged yor otherwise handled in such conveniently coiled form.

As soon as the tubing drops free the operator may press the stop-switch button 76, thereby opening the circuit to the hold-in coil 78 of the relay'77 andcausing the relay 77 to drop out, breaking the circuit to Ithe motor 13 and magnetic clutch 46. Thereupon, the operator may press the die-return switch button 75, closing the .circuit to the die-return motor 52. The opening of the relay 77 will deenergize the hold-in coil 83 of the safety inter-lock relay 82, thereby allowing vthe switch 84 to` close so that the circuit to the die-return -motor 52 will be fullycompleted upon closure of the relay 79' andthe diereturn motor 52 4will become energized and lrapidly ro- Itate the feed screw in the reverse direction. 'Since the magnetic clutch `is de-energized, the driven member will be uncoupled from the driving mem-ber 47 and the vfeed screw 4'0 will be completely under the control of the motor 52, thereby shifting the slide-block 39 down'- wardly to linitial or starting position. As soon the slide block 39 reaches its lowermost position the lower limit switch'68-will be actuated opening the circuit to the holdin coil 80 iof the die-return relay '79 causing this relay to drop out and break the circuit to the die-return motor m. The opening of this circuit is closely -timed 4so that the slide-block 39 will, at this moment, come to rest gently upon the `upper yface o'f the bracket plate 42 in substantially )precise alignment with the `lowermost or *entrant portienof the groove 46 of the drum 31 andthe machine A will -be in position for the next drawing operation.

If, for any reason, an unusually long section of tubing is being drawn so that the entire length of the groove '36 is filled and the slide-block is still moving upwardly, then the boss 70 will engage the actuatinglever 72 of the upper limit switch 71, thereby opening the 4circuit through -the hold-in lcoil -of the Vmain relay 77 in the same manner Ias would have `been accomplished if the operator had, yhimself, pressed the stop-switch button 76.

It will be understood that the machine A may be adapted for drawing any particular diameter `of tubing -by 'changing the drawing die :57 and E'the Ldrum'31. Since ythe speed of upward travel of the slide-block 39 must be different from each different size of pipe being drawn fthe sprockets 23, 25, 27, must vbe changed appropriately 'so that the speed of rotation of the drum 31 andthe -upward-rate `of travel of the slide-block 39 will -be properly `related to each other. -In other words, 'there will `be 'a set -of tools for each particular diametral size including a drum 31, drawing die 57, and companion sprockets 23, 25, 27.

It should be understood that changes and modifications in the form, construction, arrangement, and combination of the several parts of the bull-block may be made and substituted for those herein shown and described without departing from the nature and principle of our invention.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

l. A bull-block for drawing ductile tubing and the like comprising a base, a frame, driving means associated with the base, a drum operatively mounted for rotation upon the frame and drivingly connected to the driving means, said drum being provided on its peripheral face with a continuous helical groove, a slide-block shiftably mounted on the frame for movement along a path spaced outwardly from the drum and parallel to the axis of rotation thereof, a drawing die carried by the slide-block, a feed-screw journaled at its ends in outwardly spaced parallel relation to the axis of the drum and being threadedly engaged in the slide-block, and driving means for rotating the screw whereby to cause the slide-block to travel along its path in timed relation to the rotation of the drum at a speed which is matched to the pitch of the helical groove.

2. A bull-block for drawing ductile tubing and the like comprising a base, a frame, driving means associated with the base, a drum operatively mounted for rotation upon the frame and drivingly connected to the driving means, said drum being provided on its peripheral face with a continuous helical groove of arcuate cross-sectional contour conforming in shape to a segment of the external cross-sectional Shape of the tubing being drawn so as to t snugly up around and substantially support said tubing during drawing operations whereby to prevent cross-sectional deformation of said tubing as it is being drawn, a slide-block shiftably mounted on the frame for movement along a path spaced outwardly from the drum and parallel to the axis of rotation thereof, a drawing die carried by the slide-block, a feedscrew journaled at its ends in outwardly spaced parallel relation to the axis of the drum and being threadedly engaged in the slide-block, and driving means for rotating the screw whereby to cause the slide-block to travel along its path in timed relation to the rotation of the drum at a speed which is matched to the pitch of the helical groove.

3. A bull-block for drawing ductile tubing and the like comprising a base, a frame, driving means associated with the base, a drum operatively mounted for rotation upon the frame and drivingly connected to the driving means, said drum being provided on its peripheral face with a continuous helical groove of semicircular cross-sectional contour conforming in shape to a segment of the external cross-sectional shape of the tubing being drawn so as to iit snugly up around and substantially support said tubing during drawing operations whereby to prevent cross-sectional deformation of said tubing as it is being drawn, a slide-block shiftably mounted on the frame for movement along a path' spaced outwardly from the drum and parallel to the axis of rotation thereof, a drawing die carried by the slide-block, a feed-screw journaled at its ends in outwardly spaced parallel relation to the axis of the drum and being threadedly engaged in the slide-block, and driving means for rotating the screw whereby to cause the slide-block to travel along its path in timed relation to the rotation of the drum at a speed which is matched to the pitch of the helical groove.

4. A bull-block for drawing ductile tubing and th like comprising a base, a frame, driving means associated with the base, a drum operatively mounted for rotation upon the frame and drivingly connected to the driving means, said drum being provided on its peripheral face with a continuous helical groove of semicircularl cross-sectional contour 'conforming in Lshape to a segment of the external cross-sectional shape of the tubing being drawn so as to t snugly up around and substantially support said tubing during drawing operations whereby to prevent cross-sectional deformation of said tubing as it is being drawn, a slide-blockkshiftably mounted on the frame for movement along a path spaced outwardly from the drum andv parallel to the axis of rotation thereof, a drawing die carried by theA slideblock, slide-block traversing means for sliding the slideblock along its path in timed relation to the rotation of the drum, iirst slide-block driving-means for operating the yslide-block traversing means outwardly along its path from an initial position during a drawing operation, second slide-block driving means for returning the slideblock to initial position after conclusion of a drawing operation, and means for alternatively connecting the iirst and second slide-block driving means to the slideblock traversing means. p ,l v

5. A bull-block for drawing ductile tubing and the like comprising a base, a frame, driving Lmeans associated with the base, a drum .operatively mounted for rotation upon the frame and drivinglyA connected to the driving means, said drum beingl provided on its peripheral face with a continuous helical groove conforming in shape to a segment ofthe external cross-sectional shape of the tubing being drawn so as to lit snugly up around and substantially support said tubing during drawing. operations whereby to prevent cross-sectional deformation of said tubing asit is being drawn, the convolutions of said groove being closely contiguous, a slide-block shiftably mounted.` on the frame for movement along a path lspaced outwardly from the drum and parallelto the axisof rotation thereof, a drawing die carried by the slide-block, a feed-screwV journaled at its ends in outwardly spaced parallel relation to the axis of the drum and being threadedly engaged in the slideblock, and driving means for rotating thescrew whereby to cause the slide-block to travel along its path in timed relation to the rotation of the drum at a speed such that, for each full revolution of the drum, the slide-block will advance along its path by a distance substantially equal to the axial distance between twol adjacent convolutions of the groove. Y

References Cited inthe le of this patent UNITED STATESPATENTS 282,203 Leonard July 31,'1883 547,231 Schultz Oct. 1,k 1895 604,769 Lamb May 31, 1898 743,136 -Bauer Nov. 3, 1903 880,178 Thompson Feb. 25, 1908 904,836 Carlson Nov. 24, 1908 1,067,235 'Barrett July l5, 1913 1,578,351 Nullrneyer Mar. 30, 1926 1,862,267 Honig June 7, 1932 2,420,050 Maude May 6, 1947 2,584,099 Horkrader` Jan. 29, 1952 

